Biology 101 Labs

Step 1. Separation: The container of DNA will be heated into a ner boiling point to about 90 degrees Celsius using polymerase enzymes from a bacterium that is able to endure under high temperatures allowing the double structure of DNA to denature into two individual strands.

Step 2. Anneal: Once the temperature has decreased to about 55 degrees Celsius, two primers which are short segments of DNA that start the growth of the second strand will attach to the opposite ends of the two separated strands, annealing (binding) to their complementary base sequences in the DNA.

Step 3. Copy: On a small scale the temperature is again increased to about 72 degrees Celsius allowing the DNA polymerase, which are enzymes that build the DNA molecules to extend the primers because of it's construction of new nucleotides. The added nucleotides, while following the rules of complementary base pairing, attach to the original strands of DNA continuously until a whole new segment has been copied, ending the cycle of PCR.

From 1 to a billion

Scientists use PCR to be able to study DNA segments by turning one DNA strands into multiple amounts. After one PCR cycle the amount of copies doubles from 1 DNA segment to 2 to 4 to 8 to 16 to 32 and so on. Once 30 cycles have occurred at least one billion DNA copies have been made in just under a few hours, further giving reason to the 'chain reaction' in it's name. 

DNA replication in cells need certain enzymes for polymerases to work, such as the helicase which unwinds the double helix. Kary Mullis, creator of the PCR technique, used in heat substitution to the helicase to separate the DNA strand. He also used polymerase enzymes from a bacterium that lives and thrives under high temperatures to prevent the DNA polymerases to break down when exposed to heat as the strand is being separated.